1. Field of the Invention
The invention relates to a device for displacing an object, which device includes a drive device for moving the object along an axis of motion, a control unit which is coupled to the drive device, a set-point generator which is coupled to the control unit and is arranged to determine from secondary conditions a jerk set profile and set points for a plurality of sampling periods for a trajectory to be traveled and to apply the set points to the control unit per sampling period.
The invention also relates to a method of displacing an object along a trajectory by means of a drive device, in which a jerk profile and set points are determined from secondary conditions for a plurality of sampling periods for the trajectory.
2. Description of Related Art
A device of the kind set forth is known from U.S. Pat. No. 5,331,264. In the context of the present patent Application, secondary conditions are to be understood to mean initial values, final values and constraints, such as the maximum velocity, the maximum acceleration and the maximum jerk, being the derivative of the acceleration to time. Furthermore, a set profile is to be understood to mean a function of continuous time, representing the value of one of the motion variables at any sampling instant of the task to be performed.
The set-point generator of the known device is arranged to determine, prior to the displacement along the indicated trajectory, the jerk set profile and the other set points for the other motion variables for a plurality of sampling periods for the displacement of the object along the indicated trajectory and to apply the set points to the control unit per sampling period, so that the drive mechanism can displace the object along the indicated trajectory. It is a drawback of the known device that during the displacement of the object along the trajectory there is a waiting period for changing secondary conditions influencing the motion of the object. This waiting period occurs, for example in the case of a correction of the desired final position or upon adjustment of a higher maximum velocity of the object.